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Thread: Stepped up Prop Flange Bushing

  1. #1
    JrBirdman's Avatar
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    Default Stepped up Prop Flange Bushing

    I have the original O-320 that in 1955 had no suffix designation. The crankshaft prop flange has one unique bushing of the 6 total. It is "stepped up" to a larger diameter at the rear 3/8" of it's length. Goes from .63 to .68" dia. The 1956 parts manual calls out a single bushing P/N 68866 for the 68606 fixed-pitch propeller crank. The other 5 are P/N 62530. In the Parts Manual illustration you can clearly see the "step" depicted.

    Anyone recall the purpose of having the different bushing? There is no corresponding "Stepped" counterbore on the Sensenich 74DM propeller that is installed. However the prop is not the original equipment, it came from a mid '70s Cherokee.

    Thanks, REID

  2. #2
    Gilbert Pierce's Avatar
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    The purpose is to key your flywheel so the timing marks align properly with #1 Cylinder at TDC and the 25 degree timing mark.
    In other words it make sure you have the flying on in the right orientation.
    Last edited by Gilbert Pierce; 06-01-2011 at 04:06 PM.

  3. #3

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    The "step" is for the ring gear that goes behind the propeller... This orientates the gear correctly for timing the engine..... There is a small O stamped onto the face of the gear near the correct hole that goes onto the stepped bushing.

    Brian.

  4. #4

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    The "step" is for the ring gear that goes behind the propeller...

    Which I found at the first annual of my plane was off by a long way. When we did the mag timing check the timing marks were not lining up at all. Pulled the prop and flywheel and found the "keyed" bushing was pushed in and the flywheel was 2 bolt holes out of sync.

    All I can suspect is that someone needed to change the alternator belt and did not get it on correcly. I was also concerned that the dynamic balance job at some point was likely done with this "error" so I pulled the weight.

    I'm just thankful they did not try to adjust the mags to get it to work.

    Tim

  5. #5
    Throttle Pusher's Avatar
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    How can one change the prop flange bushing? Is there a tool for this? or can it be done with normal tools.

    Ken

  6. #6
    pa20's Avatar
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    Quote Originally Posted by Throttle Pusher View Post
    How can one change the prop flange bushing? Is there a tool for this? or can it be done with normal tools.
    Ken
    Ken,
    Lycoming SI 1098G (check for latest revision) covers this topic. http://www.lycoming.com/support/publ...fs/SI1098G.pdf

    The SI will answer your question in that it calls for a specific tool for replacing the bushing...."Tool No. ST-115 is used to remove and replace all propeller flange bushings."
    Mark Ohlau
    PA-20 N7744K 2018 Donation Paid

  7. #7
    Gilbert Pierce's Avatar
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    I put a socket large enough for the bushing to slide into just barely, behind the flange. Put a bolt thru the socket small end and thru the bushing. Put a nut and washer on the outboard end of the bolt and started tightening and out came the bushing, it slid into the socket large end. Installed the new one in reverse. The service bulletin does not show the service tool.

    Sockets, especially deep well, make great bushing removers and installers.
    Last edited by Gilbert Pierce; 06-02-2011 at 08:31 PM.

  8. #8
    pa20's Avatar
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    Gilbert,
    I MAY have seen it done this way...even on a Pacer that closely resembled one like mine!
    Mark Ohlau
    PA-20 N7744K 2018 Donation Paid

  9. #9
    Throttle Pusher's Avatar
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    Thanks for the info. I think the socket just might do the trick.

  10. #10

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    Default Lycoming propeller flange bushings?

    Went to swap props last night to the Borer prop and realized my O-320/150 narrow deck has a hollow crank with 2 recessed propeller flange bushings and 4 raised bushings which use 7/16" bolts instead of the 6 raised 3/8" bushings it should have.

    Called my local aircraft engine parts store and they said they couldn't help me without a part number for the bushing since there are so many options.

    So my question for you all is how do I identify the correct part number to use 3/8" bolts with my O-320?

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